Bis-amide linked rosin acid derivatives

ABSTRACT

The present invention relates to bis-amide linked rosin acid derivatives which are useful as a rubber additive. In one embodiment, the amide linked rosin acid derivative may serve as a total or partial replacement for antiozonants. The bis-amide linked rosin acids are prepared by reacting abietic acid and/or dehydroabietic acid with a diamine under amidation conditions.

BACKGROUND OF THE INVENTION

Both natural and synthetic elastomers usually require the use of processing aids to assist mechanical breakdown and compounding. Materials such as mixtures of oil soluble sulfonic acids of high molecular weight with a high boiling alcohol, paraffin oils, blends of sulfonated petroleum products and selected mineral oils are conventionally used as processing aids. Additional examples include petroleum, paraffinic and vegetable oils, coal tar, petroleum residues or pitches and naturally occurring or synthetic resins.

One advantage in using processing aids is they assist the incorporation of fillers and other ingredients with low power consumption since they reduce internal friction in calendering and extrusion. By reducing the amount of friction during compounding, the temperature of the rubber will remain lower and thus minimize the possibility of scorch.

Various types of rosin acids have been used as extenders for high molecular weight SBR. See Properties of GR-S Extended With Rosin Type Acids, L. H. Howland, J. A. Reynolds, and R. L. Provost, Industrial and Engineering Chemistry, Vol. 45, No. 5, May 1953. Whereas reasonably good cured physical properties can be obtained with the rosin type acids, there are problems associated with their use which include cure retardation, high tack and poor low temperature performance, which limit their use as an extender in rubber formulations.

U.S. Pat. No. 4,478,993 discloses the use of decarboxylated rosin acid also known as thermal oil as a total or partial replacement for oil in a rubber formulation. Compared with the use of aromatic extending oils in rubbers, decarboxylated rosin acids provide comparable processing and low temperature performance and superior abrasive resistance.

U.S. Pat. No. 4,775,496 discloses a reaction product of a rosin acid and a polyfunctional compound having at least one functional group capable of reacting with a carboxylic acid functionality and another functional group having antidegradant properties.

SUMMARY OF THE INVENTION

The present invention relates to bis-amide linked rosin acid derivatives of the formula: ##STR1## wherein R¹ and R³ may be the same or different and are selected from the group consisting of: ##STR2## or mixtures thereof and wherein R² is a divalent organic radical selected from the group consisting of (1) aromatic hydrocarbon radicals having from 6 to about 12 carbon atoms and halogenated derivatives thereof, (2) cycloalkylene radicals having from 2 to about 20 carbon atoms, C.sub.(2-8) alkylene terminated polydiorganosiloxane, and (3) divalent radicals included by the formula: ##STR3## where Q is a member selected from the group consisting of divalent radicals of the formulae: ##STR4## wherein x is whole number from 1 to 5.

DETAILED DESCRIPTION OF THE INVENTION

There is also disclosed a process for preparing rubber compositions which comprises admixing a rubber selected from the group consisting of natural rubber, homopolymers of conjugated diolefins, copolymers of conjugated diolefins and ethylenically unsaturated monomers or mixtures thereof with bis-amide linked rosin acid derivatives.

There is also disclosed a rubber composition which comprises (1) a rubber selected from the group consisting of natural rubber, homopolymers of conjugated diolefins, copolymers of conjugated diolefins and ethylenically unsaturated monomers or mixtures thereof and an amide linked rosin acid derivative of the formula: ##STR5## wherein R¹ and R³ may be the same or different and are selected from the group consisting of: ##STR6## or mixtures thereof and R² is a divalent organic radical selected from the group consisting of (1) aromatic hydrocarbon radicals having from 6 to about 12 carbon atoms and halogenated derivatives thereof, (2) cycloalkylene radicals having from 2 to about 20 carbon atoms, C.sub.(2-8) alkylene terminated polydiorganosiloxane, and (3) divalent radicals included by the formula: ##STR7## where Q is a member selected from the group consisting of divalent radicals of the formulae: ##STR8## wherein x is whole number from 1 to 5.

Preferably R² is phenylene.

The bis-amide linked rosin acid derivative is prepared by reacting a diamine compound with abietic acid or dehydroabietic acid. Abietic acid and dehydroabietic acid are derived from rosin. Rosin is a solid resinous material that occurs naturally in pine trees. The three major sources of rosin are gum rosin, wood rosin and tall oil rosin. Gum rosin is from the oleoresin extrudate of the living pine tree. Wood rosin is from the oleoresin contained in the aged stumps. Tall oil rosin is from the waste liquor recovered as a by-product in the Kraft paper industry.

The aged virgin pine stump is the source of wood rosin. The stump is allowed to remain in the ground for about ten years so that its bark and sapwood may decay and slough off to leave the heartwood rich in resin. It is known that production of pine stump rosin can be artificially stimulated by injecting the herbicide, Paraquat, into the lower portion of the tree. This treatment of the stump produces Pinex™ rosin.

Rosins derived from both oleoresin and aged stump wood are composed of approximately 90% resin acids and 10% nonacidic components. Chemical treatment of rosins, such as hydrogenation, dehydrogenation, or polymerization are known which produce modified resins.

Rosin acids are monocarboxylic acids having the typical molecular formula, C₂₀ H₃₀ O₂. The two major rosin acids that may be used to prepare the bis-amide linked rosin acid derivative are abietic acid of the structural formula: ##STR9## and dehydroabietic acid, having the structural formula: ##STR10##

These acids are generally in a mixture with various amounts of other rosin acids including levopimaric, neoabietic, palustric, tetrahydroabietic, pimaric, isopimaric, Δ-isopimaric, elliotinoic and sandaracopimaric. These acids can be used in combination with the abietic or dehydroabietic acid to form the compositions of the present invention. Therefore, in connection with the above formula, R¹ and R³ may contain the moiety derived from levopimaric, neoabietic, palustric, tetrahydroabietic, pimaric, isopimaric, Δ-isopimaric, elliotinoic or sandaracopimaric acid.

The acid number for the rosin acid may vary. Generally the acid number ranges from about 160 to about 175. Preferably the acid number is below 170 with a range of from about 165 to about 168 being particularly preferred.

The rosin acid is reacted with a diamine under suitable conditions to form a compound having two rosin moieties connected by two amide linkages. Representative diamines which may be used include m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane (commonly named 4,4'-methylenedianiline), 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether (commonly named 4,4'-oxydianiline), 1,5-diaminonaphthalene, 3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 2,4-bis(β-amino-t-butyl)toluene, bis(p-β-amino-t-butylphenyl)ether, bis(p-β-methyl-o-aminopentyl)benzene, 1,2-bis(3-aminopropoxy)ethane, benzidine, m-xylylenediamine, p-xylylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, bis(4-aminocyclohexyl)methane, 1,4-cyclohexanediamine, bis(3-aminopropyl)sulfide, bis(3-aminopropyl)tetramethyldisiloxane, bis(4-aminobutyl)tetramethyldisiloxane and mixtures of such diamines.

The rosin acid may be reacted with the diamine in a variety of mole ratios. Generally the mole ratio of rosin acid to diamine ranges from about 1.5:1 to about 2.5:1 with a range of from about 2.1:1 to about 1.9:1 being preferred.

An organic solvent may be used to dissolve the rosin acid and the diamine. The solvent is preferably inert to the amidation reaction. Illustrative of solvents suitable for use in the practice of this invention include: saturated and aromatic hydrocarbons, e.g., hexane, octane, dodecane, naphtha, decalin, tetrahydronaphthalene, kerosene, mineral oil, cyclohexane, cycloheptane, alkyl cycloalkane, benzene, toluene, xylene, alkyl-naphthalene, and the like; ethers such as tetrahydrofuran, tetrahydropyran, diethylether, 1,2-dimethoxybenzene, 1,2-diethoxybenzene, the mono- and dialkylethers of ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, dipropylene glycol, oxyethyleneoxypropylene glycol, and the like: fluorinated hydrocarbons that are inert under the reaction conditions such as perfluoroethane, monofluorobenzene, and the like. Another class of solvents are sulfones such as dimethylsulfone, diethylsulfone, diphenolsulfone, sulfolane, and the like. Mixtures of the aforementioned solvents may be employed so long as they are compatible with each other under the conditions of the reaction and will adequately dissolve the rosin acid, dissolve the diamine and not interfere with the amidation reaction.

The amidation reaction may be conducted in the presence of a catalyst to speed up the reaction. Examples of catalysts that may be used include acid catalysts such as sulfuric acid, hydrochloric acid and toluenesulfonic acid. The amount of catalyst that may be used will vary depending on the particular catalyst that is selected. For example, when an acid catalyst is used, from about 5% to about 10% by weight of the rosin acid is recommended.

The amidation reaction may be conducted over wide temperatures. The temperatures may range from moderate to an elevated temperature. In general, the amidation reaction may be conducted at a temperature of between about 150° C. to about 300° C.

The preferred temperature range is from about 175° C. to about 275° C., while the most preferred temperature range is from about 200° C. to about 250° C.

The amidation reaction may be conducted under a variety of pressures. Pressures ranging from about 0 psig to about 100 psig may be used to conduct the amidation reaction.

The amidation reaction is conducted for a period of time sufficient to produce the desired bis-amide linked rosin acid derivatives. In general, the reaction time can vary from minutes to several hours. If the more sluggish reaction conditions are selected, then the reaction time will have to be extended until the desired product is produced. It is appreciated that the residence time of the reactants will be influenced by the reaction temperature, concentration and choice of catalyst, total gas pressure, partial pressure exerted by its components, concentration and choice of solvent, and other factors. Desirably, the amidation reaction is conducted until the acid number of the products range from about 5 to about 30.

The process for the preparation of the bis-amide linked rosin acid derivatives may be carried out in a batch, semi-continuous or continuous manner. The amidation reaction may be conducted in a single reaction zone or in a plurality of reaction zones, in series or in parallel. The reaction may be conducted intermittently or continuously in an elongated tubular zone or in a series of such zones. The material of construction of the equipment should be such as to be inert during the reaction. The equipment should also be able to withstand the reaction temperatures and pressures. The reaction zone can be fitted with internal and/or external heat exchangers to control temperature fluctuations. Preferably, an agitation means is available to ensure the uniform reaction. Mixing induced by vibration, shaker, stirrer, rotating, oscillation, etc. are all illustrative of the types of agitation means which are contemplated for use in preparing the composition of the present invention. Such agitation means are available and well known to those skilled in the art.

The bis-amide linked rosin acid derivatives may be added to sulfur vulcanizable elastomers, for example, as an antidegradant or processing aid. The term "rubber" or "elastomer" as used herein embraces both natural rubber and all its various raw and reclaim forms as well as various synthetic rubbers. Representative synthetic elastomers are the homopolymerization products of butadiene and its homologues and derivatives, as for example, methylbutadiene, dimethylbutadiene, chloroprene (neoprene synthetic rubber) and pentadiene as well as copolymers such as those formed from butadiene or its homologues or derivatives with other unsaturated organic compounds. Among the latter are acetylenes, e.g., vinyl acetylene: olefins, for example, isobutylene, which copolymerizes with isoprene to form butyl rubber; vinyl compounds, for example vinylchloride, acrylic acid, acrylonitrile (which polymerizes with butadiene to form NBR), methacrylic acid and styrene, the latter compound polymerizing with butadiene to form SBR, as well as vinyl esters and various unsaturated aldehydes, ketones and ethers, e.g., acrolein, methyl isopropenyl ketone and vinylethyl ether. Also included are the various synthetic rubbers prepared by the homopolymerization of isoprene and the copolymerization of isoprene with other diolefins and various unsaturated organic compounds. Additionally, included are the synthetic rubbers such as 1,4-cis polybutadiene and 1,4-cis polyisoprene and similar synthetic rubbers such as EPDM. The preferred rubbers for use with the bis-amide linked rosin acid derivatives are natural rubber, polybutadiene, SBR and polyisoprene.

The rubber vulcanizates containing the bis-amide linked rosin acid derivatives may be used in the preparation of tires, motor mounts, rubber bushings, power belts, printing rolls, rubber shoe heels and soles, rubber floor tiles, caster wheels, elastomer seals and gaskets, conveyor belt covers, wringers, hard rubber battery cases, automobile floor mats, mud flaps for trucks, ball mill liners, and the like.

The bis-amide linked rosin acid derivatives may be used in a wide variety of proportions in the rubber and may be a substitute, in whole or part for conventional extender or process oils. By the term "extender or process oils", it is meant oils such as aromatic oils, naphthenic oils, paraffinic oils and the like as well as blends thereof. Specific examples of such oils include those largely composed of naphthenic and alkylated naphthenic hydrocarbons and mixtures thereof with various aromatic hydrocarbons. Such oils may be obtained from the high boiling fractions of the so-called naphthenic or mixed crude oils. They may comprise distillate fractions boiling above about 200° C. Suitable fractions are those at least 90 percent of which boil above about 250° C. as more volatile members may be lost during or after compounding and curing the rubber. Generally, the level of bis-amide linked rosin acid derivatives that may be added to the rubber composition may range from about 2 phr (parts per hundred rubber) to about 50 phr. Preferably the amount of bis-amide linked rosin acid derivatives that is added ranges from about 5 phr to about 35 phr.

Cure properties were determined using a Monsanto oscillating disc rheometer which was operated at a temperature of 150° C. and at a frequency of 11 hertz. A description of oscillating disc rheometers can be found in the Vanderbilt Rubber Handbook edited by Robert O. Babbit (Norwalk, Connecticut, R. T. Vanderbilt Company, Inc., 1978), pages 583-591. The use of this cure meter and standardized values read from the curve are specified in ASTM D-2084. A typical cure curve obtained on an oscillating disc rheometer is shown on page 588 of the 1978 edition of the Vanderbilt Rubber Handbook.

In such an oscillating disc rheometer, compounded rubber samples are subjected to an oscillating shearing action of constant amplitude. The torque of the oscillating disc embedded in the stalk that is being tested that is required to oscillate the rotor at the vulcanization temperature is measured. The values obtained using this cure test are very significant since changes in the rubber or the compounding recipe are very readily detected.

The following table reports cure properties that were determined from cure curves that were obtained for the two rubber formulations that were prepared. These properties include a torque minimum (Min Torque), a torque maximum (Max Torque), the total increase in torque (Delta Torque), minutes to 25% of the torque increase (t25 min.), and minutes to 90% of the torque increase (t90 min.).

Peel adhesion testing was done to determine the interfacial adhesion between various rubber formulations that were prepared. The interfacial adhesion was determined by pulling one compound away from another at a right angle to the untorn test specimen with the two ends being pulled apart at a 180° angle to each other using an Instron machine. The area of contact was determined from placement of a Mylar sheet between the compounds during cure. A window in the Mylar allowed the two materials to come into contact with each other during testing.

The following examples are presented in order to illustrate but not limit the present invention.

EXAMPLE 1

150 grams (0.5 mole) of tall oil rosin (crude abietic acid) with an acid number of 165 and 27 grams (0.25 mole) of p-phenylenediamine were added to 11 grams of toluenesulfonic acid in 100 ml of toluene. The mixture was added to a 3-neck, 1-liter flask equipped with a Dean-Stark trap, a pot thermometer and sealed with a nitrogen balloon. After 8 hours at a pot temperature of 240° C. with reflux, 11 ml of water was removed. Infrared spectroscopic analysis showed the disappearance of the acid function and formation of the bis-amide linked rosin acid derivative. The resulting heavy oil, after vacuum-oven drying at 100° C. for 8 hours, showed a high degree of tack and had a melting point just below 100° C.

EXAMPLE 2

Rubber compositions containing the materials set out in Table I were prepared in a BR Banbury using two separate stages of addition. The processing oils (naphthenic/paraffinic oil, bis-amide linked rosin acid derivative) were added to the Banbury during the first stage of mixing. The bis-amide linked rosin acid derivative was prepared in accordance with Example 1. Table II below sets out the cure behavior and vulcanizate properties for the control and the compound containing the bis-amide.

                  TABLE I                                                          ______________________________________                                                            Weight  Banbury                                             Material           Parts   Stage                                               ______________________________________                                         Natural Rubber     40.00   1                                                   BUD 1207 ®.sup.(1)                                                                            60.00   1                                                   Carbon Black       50.00   1                                                   Antiozonant/Antioxidant                                                                           4.00    1                                                   Rosin/Fatty Acids  3.00    1                                                   Wax                1.50    1                                                   Zinc Oxide         3.00    1                                                   Tackifier          4.00    1                                                   Processing Oil.sup.(2)                                                                            5.00    1                                                   Sulfur/Accelerator 2.85    2                                                   ______________________________________                                          .sup.(1) A high cis1,4-polybutadiene rubber commercially available from        The Goodyear Tire & Rubber Company.                                            .sup.(2) Naphthenic/paraffinic oil or bisamide linked rosin acid               derivative.                                                              

                  TABLE II                                                         ______________________________________                                         Cure Behavior and Vulcanizate Properties                                       ______________________________________                                                            Processing                                                                     Oil       Bis-Amide                                         ______________________________________                                         Rheometer, 150° C.                                                      Max. Torque        34.3      35.5                                              Min. Torque        8.1       8.6                                               Delta Torque       26.2      26.9                                              t90, minutes       20.8      21.1                                              t25, minutes       8.0       8.2                                               Stress Strain                                                                  Tensile Strength, MPa                                                                             10.9      10.1                                              Elongation at Break, %                                                                            438       471                                               300% Modulus, MPa  6.8       5.8                                               Peel Adhesion, 95° C.                                                                      60        60                                                To Itself, Newtons                                                             Zwick Rebound      67.7      64.9                                              100° C., %                                                              Static Ozone.sup.(1)                                                                              C3        B2                                                25% Strain, 48 hours                                                           Cyclic Ozone.sup.(2)                                                           104 hours (density/severity)                                                                      4/3       3/1                                               152 hours          Broken    4/3                                               248 hours          --        Broken                                            ______________________________________                                         .sup.(1) Static                                                                0 = No cracking                                                                               F = Complete Failure                                            Number of cracks                                                                              of cracks                                                       A = very few   1 = small (hairline)                                            (less than 1/4 surface)                                                        B = few        2 = medium                                                      (1/4 to 1/2 surface)                                                           C = moderate   3 = large                                                       (1/2 to 3/4 surface)                                                           D = heavy      4 - severe (open)                                               (3/4  to all surface)                                                          .sup.(2) Cycle D3395 - using a cycled ozone on/off procedure                   Density        Severity                                                         0 = none       0 = none                                                        1/2 = edge     1 =  .01 in.                                                    1 = 1/8 surface                                                                               3 =  .03 in.                                                    2 = 3/8 surface                                                                               5 =  .10 in.                                                    3 = 5/8 surface                                                                              10 =  .25 in.                                                    4 = 3/4 surface                                                                              12 = +.25 in.                                                   15 = broken                                                               

The bis-amide containing compound exhibits cure behavior, stress-strain properties and peel adhesion to itself similar to the control containing processing oil. The bis-amide containing compound exhibits improved static ozone resistance and superior cyclic oxone resistance when compared to the control. This result is unexpected but highly desirable incured rubber compositions. 

What is claimed is:
 1. A composition comprising a bis-amide linked rosin acid derivative of the formula: ##STR11## wherein R¹ and R³ may be the same or different and are selected from the group consisting of: ##STR12## and mixtures thereof and wherein R² is a divalent organic radical selected from the group consisting of (1) aromatic hydrocarbon radicals having from 6 to about 12 carbon atoms and halogenated derivatives thereof, (2) cycloalkylene radicals having from 6 to about 20 carbon atoms, C.sub.(2-8) alkylene terminated polydiorganosiloxane, and (3) divalent radicals included by the formula: ##STR13## where Q is a member selected from the group consisting of divalent radicals of the formulae: ##STR14## wherein x is whole number from 1 to
 5. 2. The composition of claim 1 wherein R² is a divalent organic radical selected from the group consisting of (1) aromatic hydrocarbon radicals having 6 carbon atoms and divalent radicals included by the formula: ##STR15##
 3. A process for preparing rubber compositions which comprises admixing a rubber selected from the group consisting of natural rubber, homopolymers of conjugated diolefins, copolymers of conjugated diolenfins and ethylenically unsaturated monomers or mixtures thereof with the bis-amide linked rosin acid derivative of claim
 1. 4. The process for preparing rubber compositions according to claim 3 wherein the amide linked rosin acid derivative is at a concentration of from about 2 parts per hundred rubber to 50 parts per hundred rubber and is in an intimate mixture with said rubber.
 5. The process for preparing rubber compositions according to claim 4 wherein the bis-amide linked rosin acid derivative is at a concentration of from about 5 to 35 parts per hundred rubber.
 6. The composition of claim 1 wherein said composition is added to a rubber selected from the group consisting of natural rubber, homopolymers of conjugated diolefins and copolymers of conjugated diolefins and ethylenically unsaturated monomers.
 7. The composition of claim 6 wherein said composition is at a concentration of from about 2 parts per hundred rubber to 50 parts per hundred rubber.
 8. The composition of claim 7 wherein said composition is at a concentration of from about 5 to 35 parts per hundred rubber.
 9. The composition of claim 1 wherein in addition to abietic acid or dehydroabietic acid, R¹ or R³ is also derived from an acid selected from the group consisting of levopimaric acid, neoabietic acid, palustric acid, tetrahydroabietic acid, pimaric acid, isopimaric acid, Δ-isopimaric acid, elliotinoic acid, sandaracopimaric acid, and mixtures thereof. 